rust: Fix cargo clippy and cargo doc findings

Fix the new `cargo clippy` and `cargo doc` findings that were triggered
with the recent policy addition.

Signed-off-by: Marc Hartmayer <mhartmay@linux.ibm.com>
Reviewed-by: Steffen Eiden <seiden@linux.ibm.com>
Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>

rust/pv_core/src/uvdevice/attest.rs

@@ -152,9 +152,8 @@ impl AttestationCmd {
     /// If called before a successful attestation the data in this buffer is undefined.
     pub fn additional(&mut self) -> Option<&[u8]> {
         // truncate the add size to the UV reported size
-        match &mut self.additional {
-            Some(ref mut a) => a.truncate(self.uvio_attest.add_data_len as usize),
-            None => (),
+        if let Some(ref mut a) = &mut self.additional {
+            a.truncate(self.uvio_attest.add_data_len as usize)
         }
         self.additional.as_deref()
     }

rust/pv_core/src/uvdevice/secret.rs

@@ -53,8 +53,8 @@ impl AddCmd {
     ///
     /// # Errors
     ///
-    /// This function will return an error if the provided data does not start with the
-    /// [`crate::AddSecretRequest`] magic Value.
+    /// This function will return an error if the provided data does not start
+    /// with the `AddSecretRequest` magic Value.
     pub fn new<R: Read>(bin_add_secret_req: &mut R) -> Result<Self> {
         let mut data = Vec::with_capacity(PAGESIZE);
         bin_add_secret_req.read_to_end(&mut data)?;

rust/pv_core/src/uvdevice/secret_list.rs

@@ -337,7 +337,7 @@ where
 {
     struct FieldVisitor;
 
-    impl<'de> serde::de::Visitor<'de> for FieldVisitor {
+    impl serde::de::Visitor<'_> for FieldVisitor {
         type Value = [u8; SecretId::ID_SIZE];
 
         fn expecting(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result {

rust/pv_core/src/uvsecret.rs

@@ -11,7 +11,7 @@ use byteorder::{BigEndian, ByteOrder};
 use std::{fmt::Display, mem::size_of};
 use zerocopy::{AsBytes, U16};
 
-/// The magic value used to identify an [`crate:AddSecretRequest`]
+/// The magic value used to identify an `AddSecretRequest`.
 ///
 /// The magic value is ASCII:
 /// ```rust